The midrange in many loudspeakers may suffer from timbre defects in the acoustic output at the ends of the midrange bandwidth. The timbre defects may include peaks and dips that may result from interference, constructive or destructive, from sound radiation originating in spatially diverse areas of the diaphragm. The peaks and dips may also originate from the Helmholtz cavity resonance formed by the cone shaped diaphragm itself. Although in a speaker system, the midrange transducer operation is usually band limited with frequency limiting low pass filters to operate below the frequencies where the peaks and dips manifest themselves, such filters are necessarily tapered so that the midrange sound pressure level is attenuated by between 6-24 dB SPL/doubling of frequency. As a result, midrange timbre defects found at frequencies several times the frequency of the high pass filter may affect the overall timbre performance of the loudspeaker system.
A typical loudspeaker may have increased directivity and/or nulls in the frequency response at higher frequencies. Accordingly, the speaker will not provide the same frequency response or tonal quality for each listener depending upon the listener's relative position to the speaker. The response difference may result in reduced high frequency output at some listening positions. Additionally, the response at angles away from a primary axis of the speaker may have a different character from the response on the primary axis. Typically, the different character of the off-axis performance cannot be corrected electronically.
Automotive sound systems currently suffer from different tonal balance in different listening positions due to the directivity characteristics of direct radiating loudspeakers. Sound energy radiating into the surrounding ambient space within an automobile may result in different tonal balance characteristics depending upon the relative position of the listener to the loudspeaker.